Power / EV Chargers
Installation and User Guide for DEFA MultiCharger 1204R Flex and 1204R Flex Li
Quick guide for the DEFA MultiCharger 1204R Flex and 1204R Flex Li battery chargers. Includes installation instructions, wiring diagrams, safety precautions, and technical specifications.
Table of contents
Manual images
Click an image to enlargeQuick guide from the manual
The DEFA MultiCharger 1204R Flex and 1204R Flex Li are electronic battery chargers designed for permanent installation in vehicles. They feature a 4A charging current, maintenance mode, and an integrated relay for switching engine and interior heaters. The charger requires a back voltage of approximately 2V from the battery to start charging.
Safety Instructions
- Explosive Gases: Batteries generate explosive gases during normal operation. Work in a well-ventilated area and avoid sparks, flames, or smoking near the battery.
- Grounding: The charger must be grounded. Do not alter the AC cord or plug.
- Connection: Always connect and disconnect DC output terminals only after removing the AC cord from the electric outlet.
- Battery Types: 1204R Flex supports Lead/Acid, AGM, EFB, and GEL. 1204R Flex Li supports Lithium-ion batteries with an integrated Battery Management System (BMS).
- Prohibitions: Never charge a frozen battery. Do not use the charger as a 12V power supply (battery eliminator).
Installation
Install the charger in a location away from the battery that does not exceed the length of the enclosed 12V charging cable. If the cable is extended, use a larger cross-section cable to avoid voltage drop. Secure the charger using the fastening bracket or supplied cable ties. Ensure the charger is clear of hot parts (exhaust, turbo) and moving parts (pulleys, fans).
Heater Control: To activate the engine and interior heater output, the control inlet signal (marked with a clock) must be supplied with a +12V signal. This is typically provided by the DEFA control unit's yellow cable. If no control unit is used, the provided red cap can be used to bridge this signal.
Usage
The charger operates independently of the car heating system timer. It switches to maintenance mode automatically when the battery is fully charged.
- Green pulse: Charging in progress.
- Green light: Fully charged.
- Red pulse: Error.
Technical Information
The charger operates on 100-120V AC/60Hz. The maximum charging current is 4A. Operating temperature ranges from -40°C to +50°C. The unit is tested to UL 1236, CSA C22.2#107.2, and FCC Part 15 standards.
Practical help
Common problems
Charger does not start charging
The charger requires a back voltage of approximately 2V from the battery to initiate charging. It cannot be used as a standalone 12V power supply.
Heater relay not activating
Ensure both the +12V control signal (yellow cable or red cap) and 120V power are connected to the charger.
Incorrect charging voltage
Do not cut or extend the 12V charging cable. If extension is necessary, use a cable with a larger cross-section.
Before use
- Ensure all vehicle accessories are turned off.
- Verify the battery type is compatible (LA/AGM/GEL/EFB for Flex; Li-Ion with BMS for Flex Li).
- Clean battery terminals to prevent corrosion.
- Ensure the installation area is well-ventilated.
- Check that the charger is mounted away from hot engine components like the turbo or exhaust manifold.
Specs in practice
- Maximum Charging Current
- 4A
- Operating Temperature
- -40°C to +50°C (-40°F to +122°F)
- Maintenance Charging
- 13.3-13.8V (Flex) or 13.8V (Flex Li)
- Fuse size 12V
- 7.5A
Images and diagrams
- Wiring diagrams illustrate connections for WarmUp Bluetooth systems, direct connections, and standalone setups.
- Mounting diagrams show the use of the fastening bracket and cable ties for secure installation.
Model compatibility
- 1204R Flex: Compatible with LA, GEL, EFB, and AGM batteries.
- 1204R Flex Li: Compatible with Li-Ion batteries that have an integrated Battery Management System (BMS).
Manual page author
Emily Carter
User documentation editor
Prepares concise manual descriptions and highlights the most useful setup, operation, and maintenance information for readers.